The present invention relates generally to a keyless entry system for locking and unlocking an automotive vehicle door in use with a preset code inputted by pushing push buttons on the door, instead of using a key. More particularly, the invention relates to a keyless entry system which has a variable number of code elements of the preset code.
U.S. Pat. No. 4,205,325, issued on May 27, 1980, to Haygood et al shows a keyless entry system for locking and unlocking a vehicle door lock mechanism. In Haygood et al, several functions are incorporated in a single keyless entry system for an automotive vehicle. Major improved features include a permanent preprogrammed code storage memory and a user programmable code storage memory, wherein either code may be inserted into the system to gain entry into the vehicle and enable the other functions. The other functions include the ability to unlock one or several doors of the vehicle, retract a roof-window, unlock a deck lid, lower selected side windows, reprogram a new user selected code into the programmable memory or disable the system response to the user selected code. These functions have been found to be highly desirable since they can be controlled to occur prior to entering the vehicle.
Five digit designated pushbutton keyboards on opposite vehicle doors are shown in the preferred embodiment, as the means by which all predetermined codes are manually entered into the system. A primary keyboard mounted on the left front (driver's) door is designated by the system to have continual override priority over the keyboard mounted on the right front (passenger's) door. However, each keyboard has an independent operational capability to allow a user to enter correct digit codes and to have the system perform the aforementioned functions.
In operation of Haygood et al, a depression of any pushbutton on either keyboard will cause illumination of the keyboard, activation of the system, and may also cause illumination of the vehicle interior for a predetermined period of time. In this manner, the system is visible for night operation and activated to receive a multi-digit code which corresponds to either the permanent preprogrammed code or a programmed user selected code. The user then depresses a sequence of digitally designated pushbuttons and each depression commences a new time period for illumination and activation. In order to eliminate excessive battery drain, the system will deactivate and illumination will terminate if the user hesitates longer than the predetermined time period. When proper entry of either the permanent or user selected multi-digit code is made, the door upon which the particular keyboard is mounted will immediately unlock and allow entry to the passenger compartment of the vehicle. Subsequently, while the system remains activated during the aforementioned time period, predetermined digital pushbuttons may be depressed to unlock all the other vehicle doors, unlock, the deck lid, retract a roof-window, lower the side windows, program a new user selected code into the programmable memory, or disable the system response to the last programmed user selected code.
In the particular point of the present invention, the keyless entry system is to permit a change in the individual numbers constituting the combination code, referred to hereinafter as a user's code or a second code, when utilizing a permanent code known only by the owner, referred to hereinafter as a first code. In the usual use, the vehicle door lock mechanism, the trunk lid locking mechanism and other vehicle equipment are operated using only the second code. As will be understood, the numbers of possible combinations of individual numbers constituting the code (hereinafter referred to as the code elements) is determined depending on the number of code elements to be combined. For example, assuming each code element is selected from 10 figures, e.g., 0 to 9, and four code elements are combined to constitute the code, the number of possible combinations is 10.sup.4 =10,000. If the code element is to be selected from 5 figures and six code elements are to be combined, the number of possible combinations become 5.sup.6 =15,625. Increasing the number of figures to be selected as code elements increases the space required. In turn, increasing the number of code elements increases the difficulty of memorizing and remembering the preset code. According to the present system, the preset code can be changed with respect to either the combination of code elements or the number of code elements by input means on the exterior of the vehicle without requiring special operations.
Another particular point of the present invention is that the unlocking of the door and/or trunk lid can be performed only by inputting the second code. The second code can be changed in use with the first code in such a matter that the first code is inputted in advance of changing the second code to condition the system for changing the second code. The second code may be selected at the convenience of the user. In the prior art system, unlocking the door and/or trunk lid can be performed by either of the first and second codes. Namely, unlocking can be done by two different combinations resulting in reducing security by about a half in comparison with the system using a single code. According to the present system, a circuit is provided for distinguishing the inputted code being the first code or second code.